Problem: Complete the square to solve for $x$. $x^{2}-81 = 0$
Explanation: Begin by moving the constant term to the right side of the equation. $x^2 = 81$ Take the square root of both sides. $x = \pm9$ So the solutions are: $x = 9 \text{ or } x = -9$ We already found the completed square: $( x + 0 )^2 = 81$